Map Projections/Transcript
Transcript Moby is sitting in the kitchen. He is wearing glasses and reading the newspaper. Tim is drawing on an orange with marker. TIM: Hey, remind you of anyone? An animation shows Tim presenting the orange to Moby. He has drawn a robot face on it. TIM: Beep! Beep! Beep! Tim squeezes the orange as if it's talking. Moby rolls his eyes and goes back to reading. As he turns the newspaper, a letter flies out. Tim reads from the typed letter. TIM: Dear Tim and Moby, the world map in our classroom looks way different than the one in our textbook. What's the deal, and which one's right? Thanks, Ms. Beattie's class. TIM: Actually, neither one's entirely right. The earth's surface is curved. Image shows Earth's surface from space. The sun is peeking out behind it. TIM: To recreate it on a flat piece of paper, you have to change it a little bit. So, no map can represent all of earth's features with total accuracy. The image changes to show a basic globe in a classroom, along with a pull-down map. TIM: Take this orange: Just like the earth, it's a spheroid. An animation shows Tim holding up the orange. TIM: That means it's almost perfectly round, but not quite. Now check this out. We can peel… off… the skin… but it won't lie flat. An animation shows Tim taking off the orange peel by making one vertical slit, so it's all in one piece. It's lying in a dome shape on the desk. An animation shows Tim trying to press it flat, but the peel pops back up into a dome shape. TIM: I could tear it here and here, so it flattens a bit better, but look how the parts of your face end up in the wrong spots. An animation shows Tim making two tears in the orange peel. The peel now lays more flat, but the drawing is no longer correct. The eyes and ears are uneven and stretched too far apart for the face to be recognizable. TIM: No matter how I do it, I'll end up with certain things wrong or out of place. Features might be the wrong size; An animation shows the face stretched from spherical to flat. It stretches in a way that one of the eyes is too big and the ears are too small. TIM: Or shapes might get distorted; An animation shows the face stretched in a way that the ovals for eyes are bent, the ears aren't the right shape, and the smile is too wide. TIM: Or the distance or direction between things is off. An animation shows two faces stretch from a circle to flat. On one face, the eyes and ears are too far apart and the ears are too big. On the other face, the eyes and ears are out of line with each other. TIM: The same thing happens when you transform a 3D globe into a 2D map. MOBY: Beep? TIM: Well, pulling out a globe every time you needed directions wouldn't be very practical. They're kinda tough to carry around. An animation shows a woman driving in a car with a globe on her lap. She is looking down at it with a magnifying glass. TIM: Plus it'd have to be a really big globe in order to see any kind of local detail. An animation shows the globe blowing up so large that it fills up the entire car, squishing the driver. TIM: So cartographers, people who make maps, have to find imperfect solutions. They create map projections, transferring locations from Earth onto a flat surface. An image shows a woman in a lab using an instrument to draw out a map. There are many different types of map projections on a wall behind her. Moby: Beep? TIM: Well, imagine you had a globe with a light bulb inside, and all the continents cut out. An image shows a globe with a lightbulb inside of it. Dotted lines mark the shapes of the continents that are cut out. TIM: If you put a big piece of paper next to it, the light would project the land masses onto it. An animation shows the light turning on next to a piece of paper. Beams of light come out of the globe and onto the paper in the shapes of the continents. TIM: You could touch it to a single point on the globe, and get this planar projection. An image shows the sheet of paper move so that it is above the globe. Next to this image is a map based on that placement. TIM: Or this one…Create a cone around the globe, and get this conic projection. An image shows the paper wrapped into a cone around the globe. Next to the image is the corresponding map you'd get from that viewpoint. TIM: Wrap it into a cylinder, and end up with a cylindrical projection. An image shows the paper wrapped into a cylinder that fits around the globe like a lampshade. The corresponding map appears next to it. TIM: And so on. Whatever position you pick will distort the land in different ways. MOBY: Beep? TIM: The map we're most familiar with is a cylindrical projection created way back in the 16th century. Gerardus Mercator, a European cartographer, wanted to improve the maps used on ships. An animation shows Gerardus Mercator looking out at ships in a harbor. TIM: The most popular ones at the time distorted direction. An animation shows Mercator walking into the room of a navigator looking at a map and compass. TIM: So, your destination on the map might look like it's directly north of you, An image shows a close-up on the map next to a compass. A dotted line travels from its starting point in South America to its destination directly above in North America. TIM: When in reality it's north and a little west. A split screen image shows a globe next to the map. The dotted line is diagonal and to the left to connect to the two points. TIM: To stay on course, navigators had to keep resetting their compass angle. An image shows a ship traveling up the dotted line on the map. The compass next to it needs frequent readjustment. TIM: But on the Mercator projection, direction is 100% accurate. An animation shows Mercator displaying his new map onto the wall for the navigator to see. TIM: Navigators could measure the heading between any two points… The map shows a dotted line from starting point to destination. It is a diagonal line, exactly like the one on the globe. TIM: And that's the angle they'd follow on their compass for the whole journey! An animation shows Mercator and the navigator jump up and high-five each other in front of the map. MOBY: Beep? TIM: Well, Mercator had to mess with certain elements on the globe to make his map work. He distorted its shape to fill a rectangular space. An animation shows Mercator take a globe and unroll it into a rectangle on the wall behind him. TIM: On a globe, the lines of longitude meet at the poles. An image shows the vertical lines of longitude highlight. They are curved toward the poles. TIM: Mercator straightened these out, making the lines parallel. An animation shows Mercator grab the lines on each end of the map and pull them so they are straight. TIM: Which meant he had to stretch out any features between them, too. The result was a map covered in a grid of squares. An image shows the grid between latitude and longitude lines highlight every other square. TIM: Next, Mercator adjusted the lines of latitude, running east-west. An image shows the horizontal lines of latitude highlight on the map. TIM: He spread them apart to the same degree as the lines of longitude. An animation shows Mercator physically stretch the latitude lines farther apart. As he stretches the lines, the continents stretch out accordingly. TIM: The farther lines were from the equator, the more they got spread out. Mercator didn't do any of this work physically, like we're showing here. It required a ton of complicated math to make a map with perfect direction. An animation shows Mercator sitting at an easel in a candlelit office. A globe is next to him and the walls are covered in diagrams. He is writing out an equation. MOBY: Beep? An image shows Moby pointing at a Mercator projection map and frowning. TIM: Well, I didn't say it was perfect in every way. On Mercator's map, places near the poles look much larger than they really are. That's why Greenland seems to be about the same size as Africa. An image shows a Mercator map take up the full screen. Greenland and Africa are highlighted, then stacked on top of each other. They appear to be very similar in size. TIM: But you can see on the globe that Africa is more than 10 times bigger! An image shows a globe. Africa and Greenland are highlighted again, but this time when they are stacked on top of each other Greenland is tiny in comparison. TIM: Mercator's map was an incredibly useful tool for navigating the sea. An image shows the navigator from earlier at the wheel of his ship. TIM: And you still can't beat it for accurate directions. The image changes to show the driver from earlier. Next to her is a passenger using a GPS app. TIM: A 90-degree turn on a street is a 90-degree turn on a Mercator map. An image shows a 90-degree turn approaching on the GPS map. TIM: But for learning geography, it's…it's not ideal. An images shows a global Mercator map. The continents are out of proportion. TIM: For that, you might be better off with a compromise projection. An image shows a compromise projection map. TIM: These distort all four aspects—area, distance, direction, and shape—but just a bit. So, it looks decent, and it's a good choice for visualizing global themes or landmarks. Like comparing the biggest cities, An image of the map highlights the major cities around the world. TIM: Or sorting nations by type of government. An image shows the map broken up into different colored regions based on style of government. MOBY: Beep. TIM: Equal-area projections preserve size. An image shows an equal-area projection map. TIM: Every square inch represents the same area of land or water. So these kinds of maps are great for showing things like population density. An image shows the map with icons popping up, indicating density. TIM: The tradeoff is, the shapes of land masses end up very distorted. An animation zooms in on South America on the map. It is compared side-by-side with an image of South America from a globe. The shapes are very different. TIM: Interrupted projections keep size and shape pretty accurate. Except where the map gets cut off, like in the oceans here. Plus, it's tough to measure distance and direction between different sections. An image shows an interrupted projection map. The map is missing major segments, similar to the orange peel from the beginning. MOBY: Beep! TIM: Well, like I said, there is no perfect projection. An image shows a grid of 16 different types of maps. TIM: They all contain some amount of distortion. Which can distort how we understand the world. We've already seen how one projection makes Africa look smaller than it really is. An image shows the Mercator map that causes Africa to look as big as Greenland. Africa is highlighted in orange. TIM: How might that affect our ideas about the place? An animation shows three other large continents highlighted in shades of blue. The animation switches to show four icons of people side-by-side. Three are in blue, one is orange. The orange one shrinks and the other icons look down at it. TIM: Even on maps with more accurate sizing, Western Europe is often on top and centered. An image shows a compromise projection map. Europe is highlighted in yellow. TIM: That's not reality: It's a choice, made by western cartographers. If we lived in China, the same projection might look like this. An image shows China highlighted on the map. The map shifts over, putting China in the center. TIM: And if our preferred maps had been made by people who lived south of the equator…this is how we'd probably think of our world. An animation shows the map turns upside down. MOBY: Beep. An image shows Moby holding up a figure he made out of vegetables. It resembles Tim. TIM: Uh... An animation shows Moby's chest plate open, revealing a voice meter. VOICE METER: My name's Tim. I know everything. An animation shows Moby moving the figure around as if it were the one talking. TIM: Okay, okay, I get it. VOICE METER: Everyone listen to me while I tell you about stuff. Tim sighs and leaves. Category:BrainPOP Transcripts